1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting liquid and a manufacturing method therefor.
2. Description of the Related Art
As a method of forming ink supply ports in an ink jet recording head, as described in Japanese Patent Application Laid-Open No. 2006-130868, there is a method of forming the ink supply ports by using dry etching from a rear surface of a substrate. In a case of a product such as the ink jet recording head, in which many ink supply ports are formed in a wafer, by using dry etching to form the ink supply ports, it is possible to suppress increase in opening width of the ink supply ports.
In order to form the ink supply port in the substrate to have a shape perpendicular to a surface direction, as described in Japanese Patent Application Laid-Open No. 2003-053979, a Bosch™ process is generally used, which performs coating and etching alternately. For example, by deep reactive ion etching (DRIE) using the Bosch process, a deep ink supply port having the perpendicular shape can be formed. As for the summary of the Bosch process, the following three processes, that is, (1) a process of forming a coating film by a fluorine-based material, (2) a process of removing the coating film at a bottom surface, and (3) a process of etching the substrate are mainly repeated, to thereby form a highly perpendicular shape in the substrate. More details are described below. (1) A (CF2)n-based coating film is formed on the surface by, as the fluorine-based material, a fluorocarbon gas. With this coating film, etching of a side wall is prevented in the subsequent etching process. (2) The etching gas and the fluorine-based material are replaced, and generated ions are caused to move to an engraved bottom surface. The coating film at the bottom surface is broken by the ions. (3) As an etchant, a reactive etching gas creates fluorine radicals and charged particles from SF6, and forms volatile SiFX. Those radicals etch the substrate chemically or physically, to thereby remove the substrate material.
In the Bosch process, the above-mentioned three processes are repeated. Therefore, on the side wall of the ink supply port, a ring-like repeating shape constituted by groove portions and protruding portions is formed in a depth direction of the ink supply port (see FIG. 2). Further, in a case where the process (3) has fast etching rate, the engraved amount of the groove portion becomes large, and hence the width of the ring-like repeating shape tends to increase. Hereinafter, the ring-like repeating shape constituted by the groove portions and the protruding portions is also referred to as a scallop pattern.
Generally, in order to ensure the shape formed by dry etching in the substrate surface, a stop layer having high selectivity is disposed at an etching terminal portion. The stop layer is removed by removal liquid or removal gas after the dry etching is completed. In the ink jet recording head, a flow path forming member is formed on a front surface side of the substrate, and hence, in some cases, it is difficult to remove the stop layer from the front surface side. Further, in order to use the removal gas, an apparatus for generating a large amount of fluorine-based gas is necessary. This apparatus is difficult to handle and dangerous in some cases. Therefore, it is desired that the stop layer be removed by causing the removal liquid to flow in from the ink supply port formed by dry etching from a rear surface side.
However, in the ink supply port formed by dry etching using the Bosch process, the ring-shaped scallop pattern is continuously formed in the depth direction, and hence when the removal liquid is supplied in the ink supply port, a liquid film is likely to be formed at the protruding portions of the scallop pattern. When a liquid film (hereinafter, referred to as a meniscus) is formed at the protruding portions of the scallop pattern, substitution of liquid and gas cannot be easily progressed, and in some of the supply ports, the removal liquid cannot reach the stop layer. Therefore, in some cases, fluctuations in removal of the stop layer occur. The fluctuations in removal of the stop layer lead to reduction in reliability.
Further, when the dry etching is performed in a higher rate, the engraved amount of the groove portion increases. In this case, the meniscus is more likely to be formed at the protruding portions. Further, as the size of the opening of the ink supply port becomes smaller, the meniscus is more likely to be formed. Further, as liquid having higher surface tension is used, the meniscus is more likely to be formed. As described above, there is a case where a usable range may be limited in terms of design and materials.